CN111383893B - Plasma processor and plasma control method - Google Patents

Plasma processor and plasma control method Download PDF

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CN111383893B
CN111383893B CN201811633561.XA CN201811633561A CN111383893B CN 111383893 B CN111383893 B CN 111383893B CN 201811633561 A CN201811633561 A CN 201811633561A CN 111383893 B CN111383893 B CN 111383893B
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ring
confinement
plasma
distance
frequency signal
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CN111383893A (en
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涂乐义
李双亮
梁洁
叶如彬
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Advanced Micro Fabrication Equipment Inc Shanghai
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/32009Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32082Radio frequency generated discharge
    • H01J37/32091Radio frequency generated discharge the radio frequency energy being capacitively coupled to the plasma
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32Gas-filled discharge tubes
    • H01J37/32009Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32082Radio frequency generated discharge
    • H01J37/32137Radio frequency generated discharge controlling of the discharge by modulation of energy
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/3065Plasma etching; Reactive-ion etching

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Abstract

The invention discloses a plasma processor and a method for controlling plasma leakage and discharge. A controller is arranged to be connected with the driving unit, and the controller comprises a storage unit, a measuring unit and a data retrieving unit. The measuring unit is used for measuring the safe distance between the confinement ring and the grounding ring of the plasma confinement device corresponding to the radio-frequency signals with different frequencies and powers and storing the safe distance in the storage unit, and the data retrieval unit searches the safe distance critical value corresponding to the frequency and the power radio-frequency signals in the storage unit according to the frequency and the power of the radio-frequency signals and controls the driving unit to adjust the distance between the confinement ring and the grounding ring to be within the safe distance range so as to avoid plasma leakage or discharge in a non-processing area.

Description

Plasma processor and plasma control method
Technical Field
The invention relates to the technical field of plasma etching, in particular to a plasma confinement device with continuously adjustable capacitance and a method thereof.
Background
The plasma etching technology is widely applied to the integrated circuit processing technology at present and is an essential important step in the chip processing process.
The plasma etching device utilizes the working principle of a vacuum reaction chamber to process a semiconductor substrate and a plasma flat plate substrate. The working principle of the vacuum reaction chamber is that reaction gas containing proper etchant or deposition source gas is introduced into the vacuum reaction chamber, then radio frequency energy is input into the vacuum reaction chamber to activate the reaction gas and ignite and maintain plasma, so that a material layer on the surface of a substrate is etched or deposited respectively, and then a semiconductor substrate and a plasma panel are processed. For example, capacitive plasma reactors, in which a capacitive discharge is formed between a pair of parallel electrodes when radio frequency power is applied to one or both of the electrodes, have been widely used to process semiconductor substrates and display panels.
The plasma is diffusive, and although a large portion of the plasma may remain in the processing region between a pair of electrodes, a portion of the plasma may fill the entire chamber. For example, the plasma may fill an area outside the processing region below the vacuum chamber. If the plasma reaches these areas, corrosion, deposition, or erosion of these areas may ensue, which can lead to contamination of the particles inside the reaction chamber, which in turn can reduce the reusability of the plasma processing apparatus and can shorten the operating life of the reaction chamber or reaction chamber components. If the plasma is not confined to a certain operating region, the charged particles will strike the unprotected region, which in turn leads to impurities and contamination of the semiconductor substrate surface.
Therefore, in the prior art, a plasma confinement device is usually disposed around the susceptor carrying the substrate for confining the plasma in a specific region to avoid the plasma from escaping to the region outside the processing region of the reaction chamber.
However, for a plasma processing apparatus with relatively fixed process parameters, once the plasma confinement device is determined, an ideal plasma confinement effect can be achieved, but with the continuous development of plasma processing technology, several rf power sources with different frequencies sometimes need to be applied to the same plasma processing apparatus, or the power of the rf power source needs to be adjusted during the same process. The skilled person finds that when different rf power sources are switched or the power of the same rf power source is adjusted, plasma discharge occurs in the region outside the processing region of the chamber, i.e. the plasma confinement device does not perform well the function of confining the plasma, or the reaction gas generates undesirable secondary discharge in the region outside the processing region.
Therefore, it is necessary for the skilled person to find out the cause of the secondary discharge phenomenon and the plasma leakage and to provide a plasma confinement device having a good confinement effect.
Disclosure of Invention
The invention aims to provide a plasma confinement device with continuously adjustable capacitance and a method for controlling plasma leakage or discharge, which realize effective confinement of different plasmas.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a plasma processor is disclosed, the processor comprising: the reaction cavity is internally provided with a base for bearing the substrate; at least one source radio frequency signal is applied to the reaction cavity, and the source radio frequency signal is used for generating and maintaining plasma in the reaction cavity; at least one bias radio frequency signal is applied to the pedestal; disposing a plasma confinement assembly around the pedestal, the plasma confinement assembly including a confinement ring and a ground ring; the driving unit is used for controlling and adjusting the distance between the restraint ring and the grounding ring; the detection device is arranged below the plasma confinement device and is used for detecting the plasma leakage or discharge condition; when the output power of the bias radio frequency signal is 0, the driving unit adjusts the distance between the restraint ring and the grounding ring to be larger than or equal to a first safety distance; when a source radio frequency signal with certain frequency and power is applied to the reaction cavity, the detection device cannot detect the minimum distance between the confinement ring and the grounding ring of the plasma leakage; when the output power of the bias radio frequency signal is larger than 0, the driving unit adjusts the distance between the confinement ring and the grounding ring to be larger than or equal to 0.01mm and smaller than a second safety distance, and when the bias radio frequency signal with the second safety distance being a certain frequency and power is applied to the reaction cavity, the detection device cannot detect the maximum distance between the confinement ring and the grounding ring of the plasma discharge.
Further, the driving unit is connected with a controller, the controller includes a storage unit, and the storage unit is used for storing a safe distance between the confinement ring and the grounding ring corresponding to a radio frequency signal with a certain frequency and power, and the radio frequency signal includes a source radio frequency signal and a bias radio frequency signal.
Further, the controller further comprises a measuring unit for measuring a safety distance between the confinement ring and the grounding ring when radio frequency signals of different frequencies and/or powers are applied to the reaction chamber, and storing the measured data information in the storage unit.
Further, the first safety distance is 0.1mm.
Furthermore, the controller further comprises a data retrieving unit, wherein the data retrieving unit is used for retrieving a value of a safety distance between the confinement ring and the grounding ring from the storage unit according to the input frequency and power, and controlling the driving unit to realize the adjustment of the distance between the confinement ring and the grounding ring.
Furthermore, the driving unit comprises a plurality of driving members which are uniformly distributed between the confinement ring and the grounding ring along the circumferential direction and are used for adjusting the distance between the confinement ring and the grounding ring so as to change the capacitance to ground of the confinement ring.
Furthermore, the controller is arranged outside the reaction chamber and used for controlling the driving unit in real time on line.
Further, the number of the driving members is at least 3.
Further, the driving member is an electric motor.
Furthermore, the restraining ring and the grounding ring are overlapped up and down or the grounding ring is of a U-shaped structure, and the restraining ring is placed in the grounding ring.
Further, the present invention also discloses a method of controlling plasma leakage and discharge, the method being performed in a reaction chamber of a plasma processor, the method comprising the steps of:
placing a substrate to be processed in the reaction chamber;
delivering reaction gas into the reaction cavity, and applying a source radio frequency signal to excite the reaction gas into plasma;
applying a bias radio frequency signal for increasing directionality of plasma bombardment of the substrate;
arranging a plasma confinement device, wherein the plasma confinement device comprises a confinement ring and a grounding ring;
arranging a driving unit to adjust the distance between the confinement ring and the grounding ring;
a detection device is arranged below the plasma confinement device and is used for detecting the plasma leakage or discharge condition in real time; setting the output power of the bias radio frequency signal to be 0, adjusting the distance between the confinement ring and the grounding ring to be more than or equal to a first safety distance by the driving unit, wherein when a source radio frequency signal with certain frequency and power is applied to the reaction chamber, the detection device cannot detect the minimum distance between the confinement ring and the grounding ring of plasma leakage;
when the output power of the bias radio-frequency signal is set to be larger than 0, the driving unit adjusts the distance between the confinement ring and the grounding ring to be larger than or equal to 0.01mm and smaller than a second safety distance, and when the bias radio-frequency signal with the second safety distance being a certain frequency and power is applied to the reaction cavity, the detection device cannot detect the maximum distance between the confinement ring and the grounding ring of plasma discharge.
Further, the driving unit is connected with a controller, the controller determines a safe distance between the confinement ring and the grounding ring according to the frequency and the power of the radio frequency signal applied to the reaction chamber, and controls the driving unit to adjust the distance between the confinement ring and the grounding ring to be the safe distance, wherein the radio frequency signal comprises a source radio frequency signal and a bias radio frequency signal.
Further, the controller includes a measuring unit and a storage unit, the measuring unit measures a safety distance between the confinement ring and the ground ring when radio frequency signals of different frequencies and powers are applied to the reaction chamber, and stores the measured parameter information in the storage unit.
Further, the safe distance includes a first safe distance and a second safe distance.
Further, the first safety distance is greater than or equal to 0.1mm.
Further, a source radio frequency signal is applied to the reaction chamber, the driving unit is controlled to gradually change the distance between the confinement ring and the grounding ring, a first safety distance is obtained by matching with the detection device, and the first safety distance is stored in the storage unit as the lower limit of the confinement ring and the grounding ring.
Further, the frequency and/or power of the source radio frequency signal is changed, and the first safety distance between the confinement ring and the grounding ring under different frequency and/or power conditions is measured and stored in the storage unit.
Further, a source radio frequency signal and a bias radio frequency signal are applied to the reaction chamber, the driving unit is controlled to gradually change the distance between the confinement ring and the grounding ring, the detection device is matched to obtain the second safety distance, and the second safety distance is stored in the storage unit as the upper limit of the confinement ring and the upper limit of the grounding ring.
Further, the frequencies of the source radio frequency signal and the bias radio frequency signal are kept unchanged, the power of the bias radio frequency signal is changed, and a second safety distance between the confinement ring and the grounding ring under different power conditions is measured and stored in the storage unit.
Further, the source radio frequency signal is kept unchanged, the frequency and the power of the bias radio frequency signal are changed, and a second safety distance between the confinement ring and the grounding ring under different frequency and power conditions is measured and stored in the storage unit.
Furthermore, the controller further comprises a data retrieving unit, wherein the data retrieving unit retrieves the safe distance between the confinement ring and the grounding ring from the storage unit according to the input frequency and/or power, and controls the driving unit to adjust the distance between the confinement ring and the grounding ring within a range larger than the first safe distance or larger than or equal to 0.01mm and smaller than the second safe distance.
Further, the driving unit realizes the adjustment of the distance between the confinement ring and the grounding ring by using a plurality of driving pieces arranged between the confinement ring and the grounding ring.
Further, the controller is arranged outside the reaction cavity and can control the driving unit in real time in an online manner.
The invention has the advantages that: when radio frequency signals with different frequencies and powers are applied to the reaction cavity, good plasma confinement can be performed through a determined plasma confinement device.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic diagram of a plasma processor arrangement according to the present invention;
FIG. 2 is a schematic diagram of a plasma processor arrangement according to another embodiment of the invention;
FIG. 3 is a schematic diagram of the geometry of the plasma confinement arrangement versus the plasma confinement capability;
FIG. 4 illustrates a schematic diagram of plasma sheath thickness versus plasma confinement capability;
FIGS. 5 and 6 illustrate a distance adjustable plasma confinement arrangement;
FIG. 7 shows a schematic of the construction of the controller of the present invention;
fig. 8 is a schematic diagram showing the capacitance to ground of the confinement ring as a function of the distance between the confinement ring and the grounding ring.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical solution of the present invention will be described in detail with reference to fig. 1 to 8 as specific examples. The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments.
Fig. 1 shows a schematic view of the structure of a plasma processor according to the present invention, as shown in fig. 1, the plasma processor comprising: includes a vacuum reaction chamber 100 comprising a generally cylindrical reaction chamber sidewall made of a metallic material. A gas spraying device 150 is disposed above the side wall of the reaction chamber, and the gas spraying device is connected to a gas supply device 160. The reaction gas in the gas supply device 160 enters the vacuum reaction chamber 100 through the gas shower device 150.
A susceptor 110 supporting an electrostatic chuck 115 is disposed below the vacuum reaction chamber 100, and a substrate 120 to be processed is placed on the electrostatic chuck 115. The side wall of the vacuum reaction chamber 100 is provided with a wafer transferring door 5, that is, the wafer transferring door 5 is an opening on the side wall of one side of the reaction chamber and is used for transferring the substrate between the inside and the outside of the reaction chamber. The electrostatic chuck and the base of the present invention are used as the lower plate, the gas spraying device 150 is used as the upper plate, and the distance between the two is the plate distance. The reaction gas is partially dissociated into plasma between the upper and lower plates to perform plasma processing on the substrate, and thus, a region between the upper and lower plates may be referred to as a reaction region.
The rf source power source 145 applies a source rf signal to the reaction chamber for dissociating and maintaining the reactant gas in a plasma state, the source rf signal may be applied to the upper plate or the lower plate, the embodiment of the present invention shown in fig. 1 applies the rf source power source 145 to the lower plate, the embodiment shown in fig. 2 applies the rf source power source 145 to the upper plate, and the rf source power source 145 applied to the upper plate or the lower plate does not affect its combination with the bias rf signal. The plasma 160 contains a large number of active particles such as electrons, ions, excited atoms, molecules, and radicals, which can react with the surface of the substrate to be processed in various physical and chemical reactions, so that the topography of the substrate surface is changed, i.e., the etching process is completed. An rf bias power source 146 is typically applied to the bottom plate carrying the substrate to increase the directionality of substrate bombardment by charged particles in the plasma. An exhaust pump 125 is further disposed below the vacuum reaction chamber 100 for exhausting the reaction by-products out of the vacuum reaction chamber 100.
A plasma confinement device is arranged around the lower plate and comprises a confinement ring 1 and a grounding ring 2. For exhausting the reaction byproducts to the exhaust pump 125 while confining the plasma within the processing region. The plasma confinement effect is related to the height of the confinement rings and the size of the gap, and as shown in fig. 3, the higher the height of the confinement rings or the smaller the slot gap between the rings, the better the plasma confinement effect. However, the height of the confinement rings cannot be too high due to space limitations within the reaction chamber; the size of the groove gap between the rings of the confinement rings cannot be too small, limited by the reaction by-product discharge rate and the machining difficulty. Therefore, the plasma confinement device is designed by taking the plasma confinement effect, the size of the space for accommodating the plasma confinement device, and the discharge rate of the reaction by-products into full consideration, and once the shape and size are determined, it is generally difficult to replace the plasma confinement device during the process.
As plasma technology has been developed, the number of rf power sources applied to the reaction chamber increases, and as shown in fig. 2, two rf bias power sources 146 and 147 are included, so that rf power sources with different frequencies and combinations thereof need to be selected when different process steps of a substrate are processed, or the output power of the rf power sources needs to be adjusted when the substrate is processed. At this time, the skilled person finds that a charged plasma or a plasma discharge phenomenon can be detected under the plasma confinement device when the power is switched to a certain rf frequency or adjusted to a certain frequency. Therefore, the invention provides a plasma confinement device which can meet different radio frequency and radio frequency output power without replacement.
The plasma confinement device provided by the invention can realize continuous adjustable capacitance and comprises a confinement ring 1 and a grounding ring 2 positioned below the confinement ring 1. The inner ring of the confinement ring 1 is connected with the edge ring of the electrostatic chuck, the outer ring of the confinement ring 1 is connected to the inner side wall of the plasma reaction chamber, and the space between the base and the inner side wall of the plasma reaction chamber is filled, so that plasma is prevented from leaking to an exhaust space below the confinement ring 1 along with exhaust gas from the plasma reaction chamber. In some embodiments, the grounding ring may also be provided as a U-shaped structure, the confinement ring 1 being prevented inside the U-shaped structure of the grounding ring. The confinement ring 1 is made of insulating materials such as alumina ceramics, etc., a large number of gas flow channels penetrating the upper and lower surfaces of the confinement ring are arranged on the confinement ring, and the opening size and depth of the gas flow channels are designed to ensure that all ions in the plasma gas formed above the pedestal are extinguished when the plasma gas flows through the confinement ring 1, so that the plasma gas becomes neutral gas and flows downwards. The confinement ring is arranged below the confinement ring 1, so that in order to avoid the radio frequency electric field in the base from spreading to the lower part of the confinement ring 1, reaction gas which is recovered to be neutral is discharged again, secondary plasma is formed and pollutes the inner wall and the exhaust pipeline below the reaction cavity, meanwhile, a large amount of charges accumulated on the confinement ring 1 also need to be guided to a conduction channel of a grounding end, and therefore, a grounding ring 2 (MGR ring) is arranged below the confinement ring 1, the grounding ring 2 is made of a conductor and is electrically grounded, so that radio frequency energy can be shielded above the grounding ring, secondary plasma is prevented from being generated, and meanwhile, the accumulated charges on the confinement ring 1 are guided away. In order to avoid plasma leakage, a detection device 15 is arranged below the plasma confinement device, and the detection device 15 can measure whether plasma leakage or discharge exists below the plasma confinement device in real time and send out a reminding signal in time to avoid corrosion damage to parts in a non-processing area of the reaction chamber caused by plasma leakage and discharge.
The plasma processor of the present invention further comprises a driving unit 3 for adjusting the distance between the confinement ring 1 and the ground ring 2. Fig. 5 and 6 are schematic structural diagrams illustrating a capacitance continuously adjustable plasma confinement device according to the present invention, wherein the driving unit comprises: the driving pieces are uniformly distributed between the restraint ring 1 and the grounding ring 2 along the circumferential direction and are used for adjusting the distance d between the restraint ring 1 and the grounding ring 2, so that the capacitance between the bottom of the restraint ring and the grounding ring is changed, and further, the ground capacitance C of the restraint ring 1 is changed.
It should be noted that, in order to ensure the requirement of adjusting the above-mentioned distance uniformity, the number of the driving members needs to be more than or equal to 3, and the driving members are uniformly installed between the confinement ring and the grounding ring.
Specifically, in the present embodiment, the driving member is a micro Electric motor (Electric motor), and the micro Electric motor is installed between the confinement ring and the ground ring. The invention realizes the adjustment of the ground capacitance of the confinement ring by changing the distance between the confinement ring 1 and the grounding ring 2. The inventor researches and discovers that the thickness of the plasma sheath layer is in a positive correlation with a direct current voltage Vdc on the confinement ring, and the Vdc is determined by the impedance Z of the confinement ring to the ground, and specifically, the following relations exist:
Figure BDA0001929504180000081
where ω denotes a frequency of a radio frequency signal inputted to the reaction chamber, s denotes a relative area between the confinement ring and the ground ring, and d denotes a distance between the confinement ring and the ground ring, and thus a capacitance to ground C of the confinement ring can be adjusted by adjusting a distance d between the confinement ring and the ground ring and a size of the relative area s, thereby affecting an impedance to ground Z and a voltage to ground Vpp of the confinement ring, where C = C 1 +C 2 +C 3 ,C 1 、C 3 Respectively, the capacitance between the confinement ring and the side wall of the ground ring, C 2 The capacitance between the bottom of the constraint ring and the grounding ring; in this embodimentContract C 1 、C 3 Has the following capacitance:
Figure BDA0001929504180000082
as can be seen from the above equation for the impedance Z, the frequency ω of the rf signal is inversely related to the impedance, and the plasma leakage is more likely to occur as the plasma sheath becomes thinner as the frequency ω becomes larger. And the distance between the confinement ring and the grounding ring is in a positive correlation with the impedance, and since the source rf signal is usually a high frequency signal, when only the rf source power source 145 is applied to the reaction chamber, the driving unit needs to increase the distance d between the confinement ring and the grounding ring in order to avoid plasma leakage. The detection device 15 monitors plasma leakage below the plasma confinement device in real time, a first safety distance exists when the distance d between the confinement ring and the grounding ring is adjusted, when the distance d is larger than or equal to the first safety distance, the detection device 15 cannot detect plasma leakage, and when the distance d is smaller than the lower limit, the detection device detects plasma leakage and sends out a reminding signal.
As shown in fig. 7, the present invention further includes a controller 40 connected to the driving unit 3, the controller 40 including a measuring unit 42, a storage unit 44 and a data retrieving unit 46, the measuring unit storing the above first safety distance in the storage unit 44 once it is measured. The frequency and power of the source rf signal are changed and the first safety distance between the confinement ring and the ground ring at that frequency and power is measured and stored in the storage unit 44. The data retrieving unit 46 in the controller is configured to retrieve a value of a distance between the confinement ring and the ground ring from the storage unit according to the frequency and the power of the input source radio frequency signal, and control the driving unit to adjust the distance between the confinement ring and the ground ring.
The lower limit of the safe distance may be different when source rf signals of the same frequency are applied to different plasma processors, and the present invention protects a method of controlling plasma leakage and discharge, and any safe distance measured according to the principles of the present invention falls within the scope of the present invention.
For the process of only applying the source rf signal, since the power required for generating the plasma is small, the plasma discharge problem does not need to be considered, and only the confinement effect of the plasma needs to be considered, and when the source rf signal and the bias rf signal are applied simultaneously in the reaction chamber, since the frequency of the bias rf signal is usually low, for example, lower than 15MHZ, as can be seen from the above, the plasma sheath thickness of the low frequency rf signal is large, and thus the confinement effect of the plasma is well improved. However, since the rf bias power source applies the bias rf signal to improve the directionality of the plasma bombardment, in order to improve the physical bombardment effect on the substrate, the rf bias power source needs to load a higher rf power, and during the processing process, when the power of the rf bias power source is increased, an excessively high voltage to ground on the plasma confinement device will generate a discharge phenomenon inside the plasma confinement device, resulting in a failure of low-frequency plasma confinement.
The direct reason for the discharge phenomenon in the plasma confinement device is that the pressure difference between the confinement ring and the grounding ring is too large, the pressure difference is in a negative correlation with the ground capacitance C, and when the distance between the confinement ring and the grounding ring is reduced, the pressure difference between the confinement ring and the grounding ring can be reduced, so that the discharge phenomenon between the confinement ring and the grounding ring is avoided.
Therefore, by reducing the distance d, increasing the grounding capacitance C, reducing the impedance Z to ground, reducing the voltage Vpp to ground, and blocking the discharge (light-up) between the confinement rings and the grounding ring, the confinement of the low frequency plasma is enhanced. For a low-frequency bias signal, the smaller the distance between the confinement ring and the grounding ring, the more the requirement of high output power can be met, but in order to avoid the problem that the coating on the surface of the confinement ring is consumed too fast when the confinement ring is in direct contact with the grounding ring, the distance between the confinement ring and the grounding ring is set to be greater than or equal to 0.01mm. In order to realize industrialization of the plasma processor, the storage unit is used for storing the second safety distance corresponding to the radio frequency signals under different frequencies and powers. And when a source radio frequency signal and a bias radio frequency signal are applied to the reaction cavity, controlling the driving unit to gradually change the distance between the confinement ring and the grounding ring, recording the upper limit of the second safety distance and storing the upper limit in the storage unit.
As described above, the determination of the second safety distance needs to be performed in cooperation with the detection device, the frequency and the power of the source rf signal are kept unchanged, a bias rf signal with a certain frequency and power is applied to the reaction chamber, the driving unit gradually changes the distance between the confinement ring and the grounding ring, the detection device 15 detects a discharge phenomenon when the adjustment d exceeds the second safety distance, the discharge phenomenon is not detected when the adjustment d is equal to or less than the second safety distance, and the distance d is stored in the storage unit as the upper limit of the safety distance.
The measuring unit 42 is used for controlling the application of radio frequency signals with different frequencies and powers to the reaction chamber and recording and storing the first safety distance and the second safety distance to the storage unit 44. In some embodiments, the measurement unit 42 may not be provided, and this may be done by manually adjusting the frequency and power of the rf signal.
Keeping the frequencies of a source radio frequency signal and a bias radio frequency signal unchanged, changing the power of the bias radio frequency signal, measuring a second safety distance between the restraint ring and the grounding ring under different power conditions, and storing the second safety distance in the storage unit.
Keeping the source radio frequency signal unchanged, changing the frequency and the power of the bias radio frequency signal, measuring a second safety distance between the confinement ring and the grounding ring under different frequency and power conditions, and storing the second safety distance in the storage unit.
The controller further comprises a data calling unit, the data calling unit calls a first safety distance or a second safety distance between the restraint ring and the grounding ring from the storage unit according to the input frequency and/or power, and controls the driving unit to adjust the distance between the restraint ring and the grounding ring within a range which is larger than or equal to the first safety distance or larger than or equal to 0.01mm and smaller than the second safety distance.
Based on the above principles and analysis, the following table illustratively provides relationships between frequency, power, and safety distance stored in a memory unit. The table illustratively provides 60MHz as the source radio frequency signal and 2MHz and 400KHz radio frequency signals as the bias radio frequency signal.
When a first safety distance of a source radio-frequency signal of 60MHz is measured, only the source radio-frequency signal is applied to the reaction chamber, in table 1, the storage unit stores first safety distances between the confinement ring and the grounding ring corresponding to different radio-frequency powers under the frequency of 60MHz, for example, when the frequency of the source radio-frequency signal is 60MHz and the power is 0.3KW, the distance between the confinement ring and the grounding ring is greater than 0.1mm, and when the power is increased to 3.0KW, the distance between the confinement ring and the grounding ring is increased to 0.9mm.
TABLE 1
Figure BDA0001929504180000111
And keeping the frequency and the power of the source radio frequency signal unchanged when measuring the second safety distance of the bias radio frequency signal. As shown in table 2, the storage unit stores the second safety between the confinement ring and the ground ring corresponding to different powers at frequencies of 2MHz and 400KHz, respectively. Namely, when the frequency of the selected bias radio frequency signal is 2MHz, and the output power is 5KW, the upper limit of the safety distance between the restraint ring and the grounding ring is 1.2mm, and the driving unit can drive the distance between the restraint ring and the grounding ring to be any value between 0.01mm and 1.2 mm. Similarly, when 400KHz is selected, the upper limit of the safe distance between the restraint ring and the grounding ring can be obtained according to different powers.
TABLE 2
Figure BDA0001929504180000112
Referring to fig. 5 and 6, the driving unit 3 is electrically connected to a controller 40, and the controller 40 is disposed outside the reaction chamber and is configured to control the driving unit in real time on line, that is, the driving unit can be driven in line by an electric motor to realize real-time control and segment control of plasma confinement regulation.
In this embodiment, the distance between the confinement ring and the ground ring is controlled online by installing a plurality of electric motors and combining with a controller.
Fig. 8 is a schematic diagram illustrating a change of the capacitance to ground of the confinement ring with the spacing between the confinement ring and the intermediate ring, where in actual change, assuming that the relative area S between the confinement ring and the intermediate ring is constant, a calculation formula of the capacitance to ground C of the confinement ring can be obtained through simple mathematical fitting:
Figure BDA0001929504180000113
obviously, the confinement rings have a capacitance to ground adjustable range of 1.2-6.5nF.
To obtain a larger confinement ring capacitance to facilitate confinement of the very low frequency plasma (e.g., 400K), the relative area S between the confinement ring and the intermediate ring may be increased, and then the capacitance of the FEIS ring may be adjusted using the adjustable-pitch system. It is anticipated that as the relative area is doubled, the capacitance tuning range can be: 1.3-12nF.
According to the above, a driving unit is disposed on the plasma confinement device for adjusting the distance between the beam ring and the grounding ring. The change of the capacitance of the confinement ring to the ground is realized through the adjustment of the distance. Meanwhile, a controller is arranged to be connected with the driving unit, and the controller comprises a measuring unit, a storage unit and a data retrieving unit. The measuring unit controls radio frequency signals with different frequencies and powers to be applied to the reaction cavity, and determines a safety distance critical value between the confinement ring and the grounding ring when plasma leaks or discharges under the radio frequency signal condition in cooperation with the reminding of the detection device. And the storage unit stores the frequency and the power recorded by the measuring unit and the corresponding safe distance critical value. When the plasma processor carries out process processing, the radio frequency signal required by the process is input into the data calling unit, the data calling unit searches for the safe distance critical value corresponding to the frequency and power radio frequency signal in the storage unit and controls the driving unit to adjust the distance between the confinement ring and the grounding ring to be within the safe distance range, so that plasma leakage or discharge in a non-processing area is avoided. The confinement effect of the plasma confinement device is improved.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.

Claims (23)

1. A plasma processor, characterized in that the processor comprises:
the reaction cavity is internally provided with a base for bearing the substrate;
at least one source radio frequency signal is applied to the reaction cavity, and the source radio frequency signal is used for generating and maintaining plasma in the reaction cavity;
at least one bias radio frequency signal is applied to the pedestal;
arranging a plasma confinement device around the base, wherein the plasma confinement device comprises a confinement ring and a grounding ring positioned below the confinement ring, and the confinement ring is arranged between the base and the reaction chamber;
the driving unit is used for controlling and adjusting the distance between the restraint ring and the grounding ring;
the detection device is arranged below the plasma confinement device and is used for detecting the plasma leakage or discharge condition;
when the output power of the bias radio frequency signal is 0, the driving unit adjusts the distance between the restraint ring and the grounding ring to be larger than or equal to a first safety distance; when a source radio frequency signal with certain frequency and power is applied to the reaction cavity, the detection device cannot detect the minimum distance between the confinement ring and the grounding ring of the plasma leakage;
when the output power of the bias radio frequency signal is larger than 0, the driving unit adjusts the distance between the confinement ring and the grounding ring to be larger than or equal to 0.01mm and smaller than a second safety distance, and when the bias radio frequency signal with certain frequency and power is applied to the reaction chamber, the detection device cannot detect the maximum distance between the confinement ring and the grounding ring of the plasma discharge.
2. The plasma processor of claim 1, wherein: the driving unit is connected with a controller, the controller comprises a storage unit and is used for storing a safe distance between the restraint ring and the grounding ring corresponding to a radio-frequency signal with certain frequency and power, and the radio-frequency signal comprises a source radio-frequency signal and a bias radio-frequency signal.
3. The plasma processor of claim 2, wherein: the controller also comprises a measuring unit which is used for measuring the safe distance between the restraint ring and the grounding ring when radio-frequency signals with different frequencies and/or powers are applied to the reaction cavity and storing the measured data information in the storage unit.
4. The plasma processor of claim 1, wherein: the first safety distance is 0.1mm.
5. The plasma processor of claim 2 or 3 wherein the controller further includes a data retrieval unit for retrieving from the storage unit a value of the safe distance between the confinement rings and the ground ring in dependence upon the input frequency and power, and for controlling the drive unit to effect adjustment of the distance between the confinement rings and the ground ring.
6. The plasma processor of claim 1, wherein: the driving unit comprises a plurality of driving pieces which are uniformly distributed between the restraint ring and the grounding ring along the circumferential direction and are used for adjusting the distance between the restraint ring and the grounding ring so as to change the ground capacitance of the restraint ring.
7. The plasma processor of claim 2 wherein the controller is disposed outside the reaction chamber for real time on-line control of the drive unit.
8. The plasma processor of claim 6 wherein the number of drives is at least 3.
9. The plasma processor of claim 6 wherein the drive member is an electric motor.
10. The plasma processor of claim 1, wherein: the restraint ring is overlapped with the grounding ring or the grounding ring is of a U-shaped structure, and the restraint ring is placed in the grounding ring.
11. A method of controlling plasma leakage and discharge, the method being performed in a reaction chamber of a plasma processor, the method comprising the steps of:
placing a substrate to be processed in the reaction chamber;
delivering reaction gas into the reaction cavity, and applying a source radio frequency signal to excite the reaction gas into plasma;
applying a bias radio frequency signal for increasing directionality of plasma bombardment of the substrate;
arranging a plasma confinement device, wherein the plasma confinement device comprises a confinement ring and a grounding ring positioned below the confinement ring, and the confinement ring is arranged between the base and the reaction chamber;
arranging a driving unit to adjust the distance between the confinement ring and the grounding ring;
a detection device is arranged below the plasma confinement device and is used for detecting the plasma leakage or discharge condition in real time; setting the output power of the bias radio frequency signal to be 0, adjusting the distance between the confinement ring and the grounding ring to be more than or equal to a first safety distance by the driving unit, wherein when a source radio frequency signal with certain frequency and power is applied to the reaction chamber, the detection device cannot detect the minimum distance between the confinement ring and the grounding ring of plasma leakage; when the output power of the bias radio frequency signal is set to be larger than 0, the driving unit adjusts the distance between the confinement ring and the grounding ring to be larger than or equal to 0.01mm and smaller than a second safety distance, and when the bias radio frequency signal with certain frequency and power is applied to the reaction cavity, the detection device cannot detect the maximum distance between the confinement ring and the grounding ring of plasma discharge.
12. The method of claim 11, wherein: the driving unit is connected with a controller, the controller determines the safe distance between the confinement ring and the grounding ring according to the frequency and the power of the radio-frequency signal applied to the reaction cavity, and controls the driving unit to adjust the distance between the confinement ring and the grounding ring to be the safe distance, and the radio-frequency signal comprises a source radio-frequency signal and a bias radio-frequency signal.
13. The method of claim 12, wherein: the controller comprises a measuring unit and a storage unit, wherein the measuring unit measures the safe distance between the confinement ring and the grounding ring when radio-frequency signals with different frequencies and powers are applied to the reaction chamber, and stores the measured parameter information in the storage unit.
14. The method of claim 13, wherein: the safe distance includes a first safe distance and a second safe distance.
15. The method of claim 14, wherein: the first safety distance is greater than or equal to 0.1mm.
16. The method of claim 14, wherein: applying a source radio frequency signal to the reaction cavity, controlling the driving unit to gradually change the distance between the confinement ring and the grounding ring, matching with the detection device to obtain a first safety distance, and storing the first safety distance in the storage unit as the lower limit of the confinement ring and the grounding ring.
17. The method of claim 16, wherein: changing the frequency and/or power of the source radio frequency signal, measuring a first safety distance between the confinement ring and the grounding ring under different frequency and/or power conditions, and storing the first safety distance in the storage unit.
18. The method of claim 14, wherein: and applying a source radio frequency signal and a bias radio frequency signal to the reaction cavity, controlling the driving unit to gradually change the distance between the confinement ring and the grounding ring, matching the detection device to obtain the second safety distance, and storing the second safety distance in the storage unit as the upper limit of the confinement ring and the grounding ring.
19. The method of claim 18, wherein: keeping the frequencies of a source radio frequency signal and a bias radio frequency signal unchanged, changing the power of the bias radio frequency signal, measuring a second safety distance between the confinement ring and the grounding ring under different power conditions, and storing the second safety distance in the storage unit.
20. The method of claim 19, wherein: keeping the source radio frequency signal unchanged, changing the frequency and the power of the bias radio frequency signal, measuring a second safety distance between the confinement ring and the grounding ring under different frequency and power conditions, and storing the second safety distance in the storage unit.
21. The method of any one of claims 15-20, wherein: the controller further comprises a data calling unit, the data calling unit calls the safe distance between the restraint ring and the grounding ring from the storage unit according to the input frequency and/or power, and controls the driving unit to realize the adjustment of the distance between the restraint ring and the grounding ring within the range larger than the first safe distance or larger than or equal to 0.01mm and smaller than the second safe distance.
22. The method of claim 21, wherein: the driving unit realizes the adjustment of the distance between the restraint ring and the grounding ring by using a plurality of driving pieces arranged between the restraint ring and the grounding ring.
23. The method of claim 21, wherein the controller is disposed outside the reaction chamber and is capable of real-time online control of the drive unit.
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